This invention relates to frictionally reduced hulls for marine craft as well as to hulls with decreased wave making resistance.
It has long been recognized that the performance of marine craft can be significantly improved by reducing the friction between the hull of the craft and the water. The prior art shows various ways of trying to introduce air at the interface between the hull and the body of water. For example, United States Patent Application Publication No. U.S. 2001/0022152 discloses the reduction of frictional resistance by drawing air through a conduit into a negative pressure region on the hull. However the system has certain disadvantages. It requires that the conduit project below the hull of the marine craft, thereby increasing friction. Also the air conduit must extend vertically upwards for a significant distance to a position above the water line. A mechanism must be provided to raise and lower the conduit. For example, the conduit may have to be 30 ft. long for a tanker and requires seals to prevent flooding.
The engine power or wind power required to drive a vessel through water is used approximately equally to overcome wave making resistance (50% being at the bow of the vessel) and viscous drag (50% being at the submerged hull/water interface). By comparison, superstructure resistance is minimal.
One recent method for reducing wave making resistance has been attaching a bulbous bow which increases the length of the water line, increasing buoyancy and altering the amplitude of the bow wave of the vessel.